Reading through "The Art of Electronics", I came to a statement where the writer states that the time constant (t) of RC circuit must be many times bigger than the Length of pulse you want to couple through the capacitor.
These are the words from the book:
you might use a blocking capacitor to couple pulses, or square waves. In such situations you encounter waveform distortion, in the form of “droop” and overshoot (rather than the simple amplitude attenuation and phase shift you get with sinusoidal waves). Thinking in the time domain, the criterion you use to avoid waveform distortion in a pulse of duration T is that the time constant τ=RC>>T.
Imagine a situation where I need to couple 1us rectangular pulse. Following the book, let's take time constant t=100us.
According to my understanding, time constant is the time required for the circuit to respond to the change. So, whenever the rising edge of the pulse comes in, the circuit is going to take 100us to respond. But the pulse would have already died by the time this circuit settles.
I thought this condition is valid since it wont let any fluctuations happen whenever the pulse is in either high or low state. But in the case of switching from one state to another, I think this condition is invalid.
What is the actual thing going behind the scenes?